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YOONG HOR MENG . [email protected] . 6460 6717Ngee Ann Polytechnic 1
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http://www.synvox.ch/lpc1768/lpc1768_mbed_pinout.pdf
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http://mbed.org/handbook/DigitalOut
http://mbed.org/users/yoonghm/notebook/digital-output/
DigitalOut
http://mbed.org/projects/libraries/api/mbed/trunk/wait_api
Ngee Ann Polytechnic 7
Circuit 2
mbed
p5
Circuit 1
+3.3V
mbedp5
When p5 is LOW (0 V), LED is ON When p5 is HIGH (+3.3 V), LED is ON
What is the use of the resistor?
DigitalOut
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Digital IO pins are at 3.3 V, 40 mA each, 400 mA maximum total
How do you drive an application with larger current?
http://cq.cx/interface.pl
www.youtube.com/watch?v=Te5YYVZiOKs
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Using BJT Using Darlington Pair Using Darlington Pair with Relay
Using Power MOSFET
BusOut
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#include "mbed.h"
#define WAIT_SECOND 0.1
// LSB ... MSB
BusOut Bar(p20, p19, p18, p17, p16,
p15, p14, p13, p12, p11);
DigitalOut Led(LED1);
int main() {
Led = 0;
while(1) {
// Shift from LSB to MSB
for (int i = 0; i < 10; i++) {
Led = !Led;
Bar = 1 << i;
wait(WAIT_SECOND);
}
}
}
BusOut
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#include "mbed.h"
#define WAIT_SECOND 0.1
// LSB ... MSB
BusOut Bar(p20, p19, p18, p17, p16,
p15, p14, p13, p12, p11);
DigitalOut Led(LED1);
int main() {
Led = 0;
while(1) {
// Shift from LSB to MSB
for (int i = 0; i < 10; i++) {
Led = !Led; Bar = 1 << i; wait(WAIT_SECOND);
}
// Shift from MSB to LSB
for (int i = 0; i < 10; i++) {
Led = !Led; Bar = 0x0200 >> i; wait(WAIT_SECOND);
}
}
}
BusOut
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#include "mbed.h"
#define WAIT_SECOND 0.1
// LSB ... MSB
BusOut Bar(p20, p19, p18, p17, p16,
p15, p14, p13, p12, p11);
DigitalOut Led(LED1);
int main() {
Led = 0; Bar = 3;
wait(WAIT_SECOND); // Start from LSB first
while(1) {
// Shift from LSB to MSB
for (int i = 1; i < 10; i++) {
Led = !Led; Bar = 3 << i; wait(WAIT_SECOND);
}
// Shift from MSB to LSB
for (int i = 1; i < 10; i++) {
Led = !Led; Bar = 0x0300 >> i; wait(WAIT_SECOND);
}
}
}
DigitalIn
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http://mbed.org/handbook/DigitalIn
http://mbed.org/users/yoonghm/notebook/digital-input/
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• Pin p5 is pull-up to +3.3 V (HIGH)• Negligible current flow into pin p5
+3.3V
mbedp5 S1
• Pin p5 is shorted to ground (LOW)• Resistor limits the current
// Toggle LED1 when button is pressed
#include "mbed.h"
DigitalIn enable(p5);
DigitalOut myled(LED1);
int main() {
while (1) {
if (!enable) {
myled = !myled;
wait(0.2);
}
}
}
+3.3V
mbedp5 S1
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// Toggle LED1 when button is pressed
#include "mbed.h"
DigitalIn enable(p5);
DigitalOut myled(LED1);
int main() {
while(1) {
if (enable) {
myled = !myled;
wait(0.2);
}
}
}
• Pin p5 is pull-down to ground (LOW)
+3.3V
mbed
p5 S1
• Pin p5 is connected to +3.3 V (HIGH)
+3.3V
mbed
p5 S1
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• Pin p5 is pull-up to +3.3 V (HIGH) viainternal pull-up resistor
• Pin p5 is shorted to ground (LOW)• Pull-up resistor limits the current
// Toggle LED1 when button is pressed
#include "mbed.h"
DigitalIn enable(p5);
DigitalOut myled(LED1);
int main()
{
enable.mode(PullUp);
while(1) {
if (!enable) { // p5 is +3.3 V
myled = !myled;
wait(0.2);
}
}
}
mbedp5 S1
mbedp5 S1
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• Pin p5 is pull-down to 0 V (LOW)via internal resistor
• Pin p5 is shorted to 3.3 V (HIGH)• Internal pull-down resistor limits
the current
// Toggle LED1 when button is pressed
#include "mbed.h"
DigitalIn enable(p5);
DigitalOut myled(LED1);
int main()
{
enable.mode(PullDown);
while(1) {
if (enable) { // p5 is +3.3 V
myled = !myled;
wait(0.2);
}
}
}
+3.3V
mbed
p5 S1
+3.3V
mbed
p5 S1
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ASICI/O
Devices
VCCA VCCB
If VccA is not equal to VccB
1. VOH of the driver must be greater than the VIH of the receiver
2. The VOL of the driver must be less than the VIL of the receiver
3. The output voltage from the driver must not exceed the I/O voltage tolerance of the receiver
Logic Level Translation
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http://www.nxp.com/documents/application_note/AN240.pdf
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http://mbed.org/handbook/InterruptIn
Interrupt service routine or callback
InterruptIn
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Rising Edge
http://mbed.org/users/AjK/notebook/regarding-interrupts-use-and-blocking/
InterruptIn
InterruptIn
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InterruptIn
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mbed
p5 S1
Example: Intrusion Detection Systemp5 goes low when an intrusion is detected
3.3
Voltage at pin 5
time
0
#include "mbed.h"
InterruptIn intruder(p5);
DigitalOut alarm(LED1);
DigitalOut led(LED2);
void intr() {alarm = 1; }
int main() {
intruder.mode(PullUp);
intruder.fall(&intr);
led = 1; alarm = 0; // no alarm
while (1) {
LPC_SC->PCON = 0x00;
_WFI(); // wait for interrupt
led = !led;
}
}
Ngee Ann Polytechnic 25
#include "mbed.h"
InterruptIn intruder(p5);
DigitalOut alarm(LED1);
void intr() { alarm = 1; }
int main() {
intruder.mode(PullUp);
intruder.fall(&intr);
alarm = 0; // no alarm
while (1) {
LPC_SC->PCON = 0x00;
__wfi(); // wait for interrupt
}
}
#include "mbed.h"
DigitalIn intruder(p5);
DigitalOut alarm(LED1);
int main() {
intruder.mode(PullUp);
alarm = 0; // no alarm
while (1) {
if (intruder == 0) {
alarm = 1;
}
}
}
InterruptIn
printf() malloc()
new()
wait()
__disable_irq()
__enable_irq()
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http://mbed.org/handbook/Debugging
printf(...) – Print out message on a PC terminal via USBerror(...) – Print out message on a PC terminal via USB and stop
Onboard LEDs blink blue in a distinctive pattern when it encounters run time errorThe program will stop running
You need the following software as stated in
http://mbed.org/handbook/Windows-serial-configuration
http://www.extraputty.com/
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#include "mbed.h"
DigitalOut myled1(LED1);
DigitalOut myled2(LED2);
int main() {
int i = 5;
printf("Hi!\n");
while (i--) {
myled1 = !myled1;
wait(0.25);
}
printf("Alive!\n");
while (1) {
myled2 = !myled2;
wait(0.25);
}
}
#include "mbed.h"
DigitalOut myled1(LED1);
DigitalOut myled2(LED2);
int main() {
int i = 5;
printf("Hi!\n");
while (i--) {
myled1 = !myled1;
wait(0.25);
}
error("Dead!\n");
while (1) {
myled2 = !myled2;
wait(0.25);
}
}
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Timer
Timeout
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Ticker
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AnalogIn
http://mbed.org/handbook/AnalogIn
http://mbed.org/users/yoonghm/notebook/analog-input/
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AnalogIn
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mbed
p20
GND
R1
R2
#include "mbed.h"
AnalogIn ain1(p20);
AnalogIn ain2(p19);
float vtotal;
float vr2;
int main() {
while (1){
vr2 = ain1.read() * 3.3;
vtotal = ain2.read() * 3.3;
printf("VR1 = %f ", vtotal - vr2);
printf("VR2 = %f ", vr2);
printf("VTotal= %f\n", vtotal);
wait(1.0);
}
}
VOUT
p19
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mbed p20
GND
220
100
+5V
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AnalogOut
http://mbed.org/handbook/AnalogOut
http://mbed.org/users/yoonghm/notebook/analog-output/
Change wait(0.0001) to wait(0.001) to see effect faster
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AnalogOut
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TextLCD
http://mbed.org/cookbook/Text-LCD
LCD mbed
Pin Number Pin Name Pin Number Pin Name
1 GND 1 GND
2 VCC 39 VU
3 VO 1 GND
4 RS 15 p15
5 RW 1 GND
6 E 16 p16
7 D0 Not Connected
8 D1 Not Connected
9 D2 Not Connected
10 D3 Not Connected
11 D4 17 p17
12 D5 18 p18
13 D6 19 p19
14 D7 20 p20
15 LED+ 39 VU
16 LED- 1 GND
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TextLCD
PWM1 PWM6
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PwmOut
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W = Pulse WidthT = PeriodD = Duty cycle
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PwmOut
The default period is 0.020s, pulse width is 0
PwmOut
LED1 LED4 PwmOut
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PwmOut
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#include "mbed.h"
PwmOut led1(LED1);
PwmOut led2(LED2);
PwmOut led3(LED3);
PwmOut led4(LED4);
int main()
{
while (1) {
for (float f = 0.0; f < 1.0; f += 0.001) {
led1 = f;
led2 = f * f;
led3 = (f + 1.0) / 2.0;
led4 = 1.0 - f;
wait(0.01);
}
}
}
Take note that • All LEDs are assigned values
from 0.0 to 1.0• The brightness of the LEDs color
changed abruptly
PwmOut
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#include "mbed.h"
#include <math.h>
#ifndef M_PI
#define M_PI 3.1415
#endif
PwmOut led1(LED1);
PwmOut led2(LED2);
PwmOut led3(LED3);
PwmOut led4(LED4);
int main()
{
float f = 0.0;
while (1) {
Take note that • Using 4 sinusoidal waveforms, spaced 90o apart, the
brightness of the LEDs varies smoothly• M_PI is a constant in <math.h> which is not defined in
the C library from mbed.org• All sinusoidal values are computed dynamically only when
it is needed. It is a bit CPU intensive
// Add 1.0 to ensure all values are positive
led1 = sin( (f ) * M_PI / 180.0) + 1.0;
led2 = sin( (f + 90.0) * M_PI / 180.0) + 1.0;
led3 = sin( (f + 180.0) * M_PI / 180.0) + 1.0;
led4 = sin( (f + 270.0) * M_PI / 180.0) + 1.0;
f += 1.0;
wait(0.01);
}
}
PwmOut
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#include "mbed.h"
#include <math.h>
#ifndef M_PI
#define M_PI 3.1415
#endif
#define STP 256 /* Step */
#define LED 4 /* Number of LEDs
int main()
{
PwmOut Leds[] = {(LED1), (LED2), (LED3), (LED4)};
float y[STP][LED]; // Store all values
float res = 360 / STP; // Resolution (degree per step)
float x = 0.0; // Current x
float ph = 360 / LED; // Phase different btw two successive LEDs
for (int i = 0; i < STP; i++) {
for (int j = 0; j < LED; j++) {
y[i][j] = sin( (x + ph * j) * M_PI / 180.0) + 1.0;
}
x += res; // increment x by each resolution
}
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while (1) {
for (int i = 0; i < STP; i++) {
for (int j = 0; j < LED; j++) {
Leds[j] = y[i][j];
}
count++;
wait(0.01);
}
}
}
PwmOut
Take note that • The code above run significantly faster than pervious example but consume slightly
more memory in flash and RAM
1. RX
2. TX
3. GND
Start Stop
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8-bit Data Byte
Parity
Stop
Start
Optional
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Space Space
Mark
Time
Voltage
+25V
+3V
-3V
-25V
Logic '0'
Logic '1'
Transition Region
Vcc
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Space Space
Mark
Time
Voltage
Vcc
V1H
V0L
Logic '0'
Logic '1'
Transition Region
0
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+5 V
+15 V
-15 V
t
t
1 0 0 1 1 1 1 10 0 0 0
Idle Start B0 B1 B3 B6 Stop IdleB2 B4 B5 B7
Transmission of the letter ‘J’ from μC to PC
Logic value
Meaning
Signal level at the μC output pin (TX)
Signal level at the PC input pin (RX)
ASCII character ‘J’ is represented by • 0x4A or• 01001010
μC PC
Level Shifter
TX
RX
RX
TX
TX
RX
RX
TX
LSB MSB
LSBMSB
Serial
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mbed Device
p9(TX)
p10(RX)
RX
TX
PCUSB
Serial
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http://www.ftdichip.com/Products/Cables/USBTTLSerial.htm
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If both devices are from the same power source, use CMOS Output.In this case, the input current to the microcontroller is actually taken from the +3V, and via the Source terminal of the MOSFET of the OUT pin of the Voltage Detector.
If both devices are from different power sources, use Open Drain Output.In this case, the input current to the microcontroller is actually taken from +5V, and via the Drain terminal of the N-channel MOSFET of the OUT pin of the Voltage Detector. A resistor is necessary to reduce the amount of current drawn.
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